Gasifier

ABSTRACT

A gasifier for producing synthesis gas from a widely varying feedstock of waste and natural fuels, the gasifier including an induction furnace, a molten bed and slag reaction chamber mounted on top of the induction furnace, an opening fluidly connecting the molten metal and slag with the interior of the induction furnace and the inside bottom of the reaction chamber, the reaction chamber further containing a froth and off-take reaction zones above the molten metal and slag, and a lid at the top of the reaction chamber for enclosing the reaction chamber and collecting the heat and fuel gas produced therein.

FIELD OF INVENTION

The present invention relates to a gasifier for producing synthesis gas,and in particular to a molten bed reaction chamber for producing a highquality synthesis gas from a widely varying feedstock of waste andnatural fuels, the reaction chamber being mounted on top of and in fluidwith communication with an induction furnace.

BACKGROUND OF INVENTION

Conventional gasification is a process that converts carbonaceousmaterials, such as coal, petroleum, petroleum coke or biomass, intocarbon monoxide, hydrogen and carbon dioxide. In a conventionalgasifier, the carbonaceous material undergoes three processes includingpyrolysis, combustion and gasification. During the pyrolysis process,the carbonaceous material heats up, volatiles are released and char isproduced. The process is dependent on the properties of the carbonaceousmaterial and determines the structure and composition of the char, whichwill then undergo gasification reactions. The combustion process occursas the volatile products and some of the char reacts with oxygen to formcarbon dioxide and carbon monoxide, which provides heat for thesubsequent gasification reactions. The gasification process occurs asthe char reacts with carbon dioxide and steam to produce carbon monoxideand hydrogen. The resulting gas is called syngas. Syngas is typicallycombusted in a gas turbine, and the heat is used to produce steam todrive a steam turbine.

There are four basic types of gasifiers operating today including fixedbed systems, fluidized bed systems, entrained flow systems and moltenbed systems. In a fixed bed reactor, a reactive gas or gases are passedthrough a fixed bed of feedstock in a co-current or counter currentflow. The fixed bed consists of carbonaceous fuel (e.g. coal or biomass)through which a “gasification agent” (steam, oxygen and/or air) flows ina co-current or counter-current configuration. The ash is either removeddry or as a slag. The nature of a fixed bed gasifier means that the fuelmust have high mechanical strength and must be non-caking so that itwill form a permeable bed. Thus, certain feedstocks such processedmunicipal solid waste, biosolids, ground coal and certain types ofbiomass are not suited for use in fixed bed reactors. This isparticularly true when moisture is present.

In a fluidized bed reactor, the pressure drop of the gasifying reactantsis adjusted so that the feedstock is lifted or suspended by the gaseousphase. In particular, the carbonaceous fuel is fluidized in oxygen (orair) and steam. The ash is removed dry or as heavy agglomerates thatdefluidize. The temperatures are relatively low in dry ash gasifiers, sothe fuel must be highly reactive; low-grade coals are particularlysuitable. Fluidized bed gasifiers are most useful for fuels that formhighly corrosive ash that would damage the walls of slagging gasifiers.Biomass fuels generally contain high levels of corrosive ash.

In an entrained bed reactor the solid particulate feedstock are carriedor “entrained” through the reactor by the reacting gases. In particular,a dry pulverized solid, an atomized liquid carbonaceous fuel or a fuelslurry is gasified with oxygen in co-current flow. The gasificationreactions take place in a dense cloud of very fine particles. Most coalsare suitable for this type of gasifier because of the high operatingtemperatures and because the coal particles are well separated from oneanother. The fuel particles must be much smaller than for other types ofgasifiers. This means the fuel must be pulverized, which requiressomewhat more energy than for the other types of gasifiers. It alsomeans that feedstocks such as processed municipal solid waste, certainbiomass, spent tires and several types of industrial wastes are not wellsuited for this type of gasifier.

In a molten bed reactor higher heat value feedstock (primarily coal) isinjected into a molten bath of iron, salt or coal ash contained within areactor. A reactive gas such as oxygen, steam and/or carbon dioxide isinjected into the vessel to control the rate of reaction within thereactor. A shortcoming of current molten bed gasifiers is the inabilityto process low heat value feedstocks and thus widely varying feedstocks.Often this is because low heat value feedstocks such as municipal solidwaste, certain biomass wastes and some household and industrial wastes,when introduced into a molten bath can consume rather than produce heatthus limiting the efficiency of the reactor and possibly endangering thecontinuity of the process itself.

An exemplary molten bed reactor is described in U.S. Pat. No. 4,649,867including a substantially cylindrical vessel which has a substantiallyoblong section and lateral walls and a bottom wall which are lined witha refractory lining. An orifice for discharging the bath of liquid metaland an orifice for discharging slag supernatant on the bath of liquidmetal are provided. In addition, a dome is positioned in a sealed manneron the vessel having in its upper part in the vicinity of one of theends of the vessel a sealed box for introducing an injecting branch. Anorifice is provided in the upper part of the vessel for exhausting thegases produced. A roughly central orifice for introducing additionalelements is also provided in the upper part.

Another exemplary molten bed reactor is described in U.S. Pat. No.4,865,626. This patent discloses a process for producing gas containingcarbon monoxide and hydrogen gas including introducing lump coal bymeans of a down pipe and one or more inlets in a gasifier head into agasifier having a fluidized bed region and a free board space or killingregion. The coal passes through the killing region into the fluidizedbed region and is gasified therein with the aid of oxygen oroxygen-containing gas supplied from an oxygen source and blown into aregion below the fluidized bed region. When the coal passes through thefree board space it is spontaneously dried and degassed in anendothermic reaction that results in a temperature drop in the freeboard space and ensures that only coal constituents bringing about ahigh gasification temperature enter the lower part of the fluidized bedregion.

SUMMARY OF THE INVENTION

The motivating object of the present invention was the need for asuperior waste to energy conversion process allowing for increased fuelflexibility. Specifically, for this invention, the goal is toefficiently and economically produce a high quality synthesis gas fromlow heat value, widely varying feedstock. Such feedstock can includewaste materials contaminated with inorganics as well as low gradenatural fuels and industrial by-products. The resulting synthesis gas isof sufficient quality to allow production of electrical power, refiningof Fischer-Tropsch liquids, production of methanol or the separation ofindustrial grade hydrogen. In addition, the present invention providesfor improved environmental impact and clean and more environmentallyfriendly energy production while improving upon current industrialconversion efficiencies. Further, the present invention provides a majornew source of energy from material that is currently considered useless,hazardous or not worth harvesting.

By fuel flexibility it is meant that the gasifier of the presentinvention is capable of handling a broad range of wastes from municipalwaste, medical waste, biomass to bio-solids, spent tires, andindustrial/agriculture waste. This includes a wide range of naturalfuels and waste fuels. Further, the gasifier of the present inventioncan process solids, liquids and gaseous feed streams simultaneously in asingle reactor, as well as low heat value feed (3,800 BTU/lb) as rawmaterial. Additionally, the gasifier can tolerate a large content ofin-organics and contaminants in the carbonaceous feedstock.

By efficiency and economics it is meant that the gasifier exhibits ahigh thermal conversion efficiency of about 58% to about 65% whileoperating at ambient pressure, using no air and efficiently usingoxygen. It also means that the gasifier can processes large quantities(up to 700 tons per day) of varying feedstock in a single reactorvessel. Further, the gasifier can maintain an exothermic reaction state,thus requiring minimal external heat assist, and generate high qualitysynthesis gas (250-350 BTU/scf) with a low particulate level.

By environmental impact it is meant that the gasifier produces no char,minimal ash, no tar, no oils, no phenols and no ammonia while producinguseable by-products such as siliceous slag and pig iron. The gasifiercan also efficiently and safely processes high sulfur and contaminatedcoal and several types of industrial and household hazardous waste.Further, the gasifier can recycle and dissociate polluting exhaust gasesand green house gases such as carbon dioxide, dioxins, furans, volatilesorganic gaseous compounds, nitrous oxides and the like.

In order to meet the objects of the invention there is provided a moltenbed reactor or gasifier including reaction chamber, for the productionand collection of a fuel gas, mounted on top of, in fluid communicationwith and removed from a furnace. Preferably, the furnace is an inductionfurnace, and more preferably a coreless induction furnace, although achannel induction furnace can be used. The purpose of the furnace is toprovide the reaction chamber with a constant source of molten metal,maintain the molten metal at a desired temperature, especially whensynthesis gas production within the reaction chamber becomes endothermicdue to the presence of low heat value feed, and impart vertical stirringof the molten metal within the reaction chamber for providing efficientconversion of carbonaceous fuel to carbon monoxide and hydrogen gas.Until now, induction furnaces were used primarily for batch processesinvolving melting and alloying metals.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front elevational view of a gasifier in accordance with apreferred embodiment of the present invention.

FIG. 2 is a side elevational view of the gasifier of FIG. 1.

FIG. 3 is a vertical sectional view of the gasifier of FIG. 1.

FIG. 4 is a vertical sectional view of the gasifier of FIG. 1 showingthe chemical reactions that take place within specific locations withinthe gasifier during gasification.

FIG. 5 is a front elevational view of a gasifier in accordance withanother preferred embodiment of the present invention.

FIG. 6 is a bottom plan view the gasifier of FIG. 5.

DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 4 illustrate a gasifier 10 in accordance with apreferred embodiment of the present invention. FIGS. 5 and 6 illustratea gasifier 100 in accordance with another preferred embodiment of thepresent invention. Like portions of gasifier 10 share like numberingwith gasifier 100.

The present invention is directed to an integrated, multi-stagegasification system designed to maximize the production of synthesis gasfrom a widely ranging continuous feed stream of both organic andinorganic material. Specifically, seven distinct hardware sections areintegrated into a continuous, interactive process designed to gasifysolid, liquid and gaseous hydrocarbon material simultaneously. This isdone in the presence of inorganic material which would otherwise disrupta normal gasification process. The feed stream material includes, but isnot limited to the mixed waste and natural fuels material of Table 1.

TABLE 1 SOLIDS LIQUIDS GASES Raw Waste Process Raw Waste Process RawWaste Process Material By-Products Material By-Products MaterialBy-Products Municipal Waxes Paints Waxes Landfill Gas Light Solid WastePropane Gas (MSW) (Refineries) Medical Glycerins Vegetable Oil GlycerinsSewage Gas Carbon Waste Dioxide Household Contaminated Mineral OilPetro- Contaminated Coke Oven Hazardous Carbon Chemicals Water Vapor GasWaste (HHW) Spent Tires Contaminated Contaminated Bottom Oil HydrogenDigester Filters Fuels Sulfide Gas Biomass Petroleum IndustrialContaminated Coke Solvents Fuels Bio-solids Construction HHW GasifierOils Materials Low Sulfur Tars Poly Coal Chlorinated Butylenes BrownCoal Asphalt High Sulfur Agricultural Coal Waste

Each hardware section, or process stage, is designed to accommodate aspecific group of feed stream constituents. The arrangement and designof these hardware sections is based upon generating maximum quantitiesof quality synthesis gas at minimum operational cost. Depending upon thecombination of material to be gasified, the best section of the gasifieris selected for material feed in accordance with maintaining thebalanced combination of hydrocarbons, carbonaceous materials andreaction gases. This allows control of the overall process as anexothermic reaction, resulting in maximum generation of synthesis gasfor minimum expenditure of energy.

The following description of the preferred embodiments is merelyexemplary in nature and is not intended to limit the invention, itsapplication or uses.

In FIGS. 1 and 2 there is shown a front elevation of a gasifier 10,which consists of a refractory lined lid 11, an expanded diameter,increased height reaction vessel 12, an induction furnace 13 mountedbelow and integral with the reaction vessel 12 and a tilt frame 14. Tiltframe 14 consists of a base plate 15, two vertical columns 16, gussets17 and two hydraulic cylinders 18 to tilt gasifier 10 for maintenance.

As illustrated in FIG. 3, refractory lined lid 11 is fitted with anexhaust plenum 21 to remove the synthesis gas 22, one or more top lances23 to introduce oxygen, carbon dioxide, steam, other gases or liquids 24and solid material feed 25 into the gasifier, one or more devices tomeasure the temperature 26 in the gasifier, one or more devices tomeasure the gas composition 27 and a burner port 28 to house a burnerfor preheating the gasifier. Exhaust plenum 21 includes a refractorylining 29 for preventing heat loss therethrough.

Reaction vessel 12 is fitted with a refractory lining 31 to contain amolten metal 32, a slag 33, a froth 34 and a off-take region 47. Excessslag 33 is continuously removed from the vessel by means of a siphonstagger 35. The solid material feed 25 is introduced from above by meansof one or more top lances 23 through lid 11 or through exhaust plenum 21and lid 11. Solid, liquid or gaseous feed 36 is also introduced by meansof one or more side wall injectors 37. Gaseous and liquid feed can alsobe introduced into froth 34 or off-take region 47 utilizing injectorports located along the side walls of top injection lances 23. On theside walls of top lances 23, one or more side wall ports 48 located infroth 34 and one or more side wall ports 49 located in off-take region47 can be effectively utilized due to the expanded diameter andincreased height (freeboard) of reaction vessel 12. The bottom ofreaction vessel 12 is fitted with a water cooled flange 38 to whichfurnace 13 is attached. One or more bottom injector lances 50 can alsobe utilized to enhance the mixing action and gasification process frombelow, again due to the expanded diameter of reaction vessel 12. Solids,liquids or gases may also be introduced through bottom injector lances50.

Preferably, furnace 13 is a coreless induction furnace. The heart of acoreless induction furnace is the coil, which consists of a hollowsection of heavy duty, high conductivity copper tubing which is woundinto a helical coil. Coil shape is contained within a steel shell andmagnetic shielding is used to prevent heating of the supporting shell.To protect it from overheating, the coil is water-cooled, the waterbeing re-circulated and cooled in a cooling tower or chiller.

A channel induction furnace can also be used. Channel furnaces howeverconsist of a refractory lined steel shell which contains the moltenmetal. Attached to the steel shell and connected by a throat is aninduction unit which forms the melting component of the furnace. Theinduction unit consists of an iron core in the form of a ring aroundwhich a primary induction coil is wound. This assembly forms a simpletransformer in which the molten metal loops comprise the secondarycomponent. The heat generated within the loop causes the metal tocirculate into the main well of the furnace. The circulation of themolten metal effects a useful stirring action in the melt. Channelfurnaces however suffer the drawback of requiring an initial moltenmetal charge from another source for cold start. In addition, for normaloperation, the feed rate of the carbonaceous material and reaction gasesis balanced so that the molten iron retains its high carbon content.This allows operation in the optimum portion of the Fe—C EquilibriumChart. If this balance should be temporarily lost, and the carbon isdepleted from the molten iron, then steel will be made in the bath. Thiswould require a notable increase in temperature to maintain the moltenstate of the metal while high purity carbon is injected back into thebath to restore the iron. This additional heat requirement wouldseverely strain most channel furnaces. In many cases the channel furnacewould have to be shutdown and recharged from a cold start. There is nosuch problem with a coreless induction furnace which could maintain therequired higher temperatures. This ability to sustain continuousoperation in the presence of highly varying reactions and feed streamsis critical to the overall efficiency and economics of the process.Finally, channel furnaces require additional molten iron depth in orderto avoid oxide build up or clogging in the refractory channels. Thisadditional iron is not conducive to the basic gasification reactionefficiency. Therefore, coreless induction furnaces provide a preferredflexibility and adaptability not found in channel furnaces.

A second embodiment of this design is shown in FIGS. 5 and 6. Thisconfiguration utilizes three induction furnaces 13 on a larger reactionvessel 12 to facilitate a larger molten bath to enable higher capacitymaterial throughputs. Variations in this approach can accommodate 2 orup to 6 induction furnaces 13 for a single reaction vessel 12. The useof multiple induction furnaces 13 for larger reaction vessels 12 allowsuniform stirring action and heat distribution, thus enhancing thesynthesis gas reaction and avoiding cold spots in the larger moltenmetal volume. Further, since induction furnaces are single phasedevices, each inductor can be connected to one of the three phases of astandard three phase industrial power supply. Thus, use of a phasebalancer can be eliminated. As a result, this approach also savesequipment costs while increasing electrical efficiency. In addition,this larger reaction vessel 12 does not utilize a tilt frame foremptying and maintenance, but rather uses a series of tap holes to saveon cost and complexity of design. Excess slag during operation is stillremoved by a siphon stagger.

The purpose of induction furnace 13 is to initially melt the solid pigiron and to subsequently stir molten metal 32 during operation.Induction furnace 13 is fitted with a refractory lining 42 whichcontains molten metal 32. Surrounding refractory lining 42 is a coil 43which is supported by magnetic shunts 44 which are supported by shuntbolts 45 which fasten to a furnace cage 46.

The manner in which gasifier 10 is started is as follows. Once gasifier10 has been charged with solid pig iron, reaction vessel 12 is preheatedto about 2200° F. by means of a gas burner inserted through burner port28 or alternately through a top mounted port for a lance 23. Electricalpower is then applied to induction furnace 13 which melts and superheatsmolten metal 32 to about 2700° F. The frequencies used for inductionmelting vary from 50 cycles per second to 10,000 cycles per second. Thehigher the operating frequency, the greater the maximum amount of powerthat can be applied to induction furnace 13 and the lower the amount ofturbulence induced.

When the charge material is molten, the interaction of the magneticfield and the electrical currents flowing in induction coil 43 produce astirring action within molten metal 32. This stirring action forcesmolten metal 32 to rise upwards into reaction vessel 12. The degree ofstirring action is influenced by the power and frequency applied as wellas the size and shape of coil 43 and the density and viscosity of moltenmetal 32. The stirring action within the molten metal bath is importantas it helps with mixing of molten metal 32 as well as homogenizing oftemperature throughout induction furnace 13 and reaction vessel 12.

FIG. 4 illustrates a cross section of a gasifier 10 showing the chemicalreactions that take place therein. Oxygen is introduced into moltenmetal 32 by means of one or more oxygen lances 23. As the oxygenimpinges on molten metal 32, which initially consisted of iron, carbonand silicon, the oxygen initially oxidizes the iron to iron oxide asfollows:

2Fe+O₂=>2FeO   (1)

The silicon dissolved in molten metal 32 is then oxidized to silicondioxide as follows:

Si+2FeO=>SiO2+2Fe   (2)

Likewise, the carbon dissolved in molten metal 32 is then oxidized tocarbon monoxide as follows:

C+FeO=>CO+Fe   (3)

The oxidation of the iron to iron oxide and silicon to silicon dioxideinvolves minimal volumetric change. However, as the carbon is oxidizedto carbon monoxide, there is a significant increase in volume when asolid is oxidized to a gas. This volumetric expansion causes moltenmetal 32, the liquid iron oxide, the liquid silicon dioxide and slag 33to form froth 34.

If the carbon is not replenished, the oxygen will remove virtually allof the carbon in molten metal 32 in about fifteen minutes. Thereafter,froth 34 will collapse and the iron will be completely oxidized to ironoxide. To maintain froth 34 and molten metal 32, the carbon must beinjected at a rate equal to the rate at which the carbon is beingremoved by oxidation, as follows:

FeO+C=>CO+Fe   (4)

This insures that the iron that was oxidized to iron oxide is thensubsequently reduced by the carbon returning most of the iron to moltenmetal 32 so that it can subsequently be re-oxidized thereby allowing thecycle to repeat indefinitely. This continuous recycling is important tothe efficiency of the process. Since some of the iron oxide will becarried out of reactor vessel 12 as part of slag 33, there will be adepletion of molten metal 32. Consequently, the iron will have to beadded to reactor vessel 12 to maintain the required level of moltenmetal 32 in the gasifier.

As solid feed 25 is injected into molten metal 32, some of it willdissociate into the carbon and hydrogen and some will remain as ahydrocarbon. Likewise, as liquid or gaseous feed 36 is injected intofroth 34, slag 33 or molten metal 32, some of it will dissociate intocarbon and hydrogen and some will remain as a hydrocarbon. That portionof feeds 25 and 36 that dissociates will cause molten metal 32 to frothas the hydrogen is released as a gas. To dissociate feeds 25 and 36,heat must be provided, as follows:

Feeds (25 and 36)+heat=>C+H₂   (5)

Likewise, that portion of feeds 25 and 36 that is oxidized to carbonmonoxide, carbon dioxide and water vapor by the oxygen will cause moltenmetal 32 to froth.

Feeds (25 and 36)+Oxygen=>Synthesis Gas   (6)

2C+2H₂+2O₂=>CO+CO₂+H₂+H₂O+Heat   (6a)

The frothing process is most important since it increases the surfacearea for the following reaction.

Feeds (25 and 36)+Iron Oxide=>Synthesis Gas   (7)

2C+2H₂+4FeO=>CO+CO₂+H₂+H₂O+4Fe+Heat   (7a)

The amount of oxygen added is closely controlled so that the heatreleased will provide the heat to dissociate feeds 25 and 36 and providethe heat required to elevate the synthesis gas to a temperature highenough to keep froth 34, slag 33 and metal 32 molten. The operatingtemperature will be in the range of 2700-3000° F.

The resulting synthesis gas consists of carbon monoxide, carbon dioxide,hydrogen and water vapor. The ratio of the products in the synthesis gasis controlled by the following equilibrium:

CO+H₂O=CO2+H₂   (8)

The equilibrium constant for equation 7 is equal to:

k=[pCO₂ ×pH₂ ]÷[pCO×pH₂O]=[6355÷(−R×T]−[6.24÷(−R×T)]  (9)

Where p=Pressure

R=Gas Costant

T=Temperature

Since the equilibrium constant k is temperature dependent, thepercentage of each gas will vary with temperature. The higher thetemperature the greater the amounts of carbon monoxide and water vapor.Conversely, the lower the temperature, the greater the amounts of carbondioxide and hydrogen. The ratio of carbon compounds formed to thehydrogen compounds formed is directly proportional to the amount ofcarbon and hydrogen in feeds 25 and 36.

Reaction vessel 12 is maintained under either a slightly negative,neutral or slightly positive pressure to remove the hot synthesis gasvia exhaust plenum 21 while maintaining the proper reaction anddiffusion of gases from molten metal 32 and slag 33. Exhaust plenum 21is refractory lined 29 since the synthesis gas exits at temperatures ashigh as 2700 to 3000° F.

Because feeds 25 and 36 contain some metallic elements, they oxidize andbecome part of slag 33 or molten metal 32. When these metal oxides causeslag 33 to go basic, silica sand can be added to keep slag 33 fluid.Conversely, when these metal oxides cause slag 33 to go acidic,dolomitic limestone can be added to lower the melting point of slag 33to keep it fluid. It should be noted that slag chemistry in this processis important as it relates to the viscosity of slag 33 and the necessityof controlling the continuity of the synthesis gas production. Inaddition, just as in a metal refining process, the chemistry of slag 33is related to the removal of detrimental impurities. In the synthesisgas production, it is advantageous to keep any impurities, such assulfur and phosphorous, in metal bath 32 or capture these impurities inslag layer 33 rather than having to remove them from the gas stream insome later step. The slag chemistry is monitored by periodic samplingand computer control. Siphon type stagger 35 is employed to continuouslyremove excess slag 33. Most heavy metals, if present in the feed stream,can also be captured by the molten metal or slag regimes.

The following paragraphs now explain important features of each majorhardware section.

Induction Furnace Induction furnace 13 is integral with but separatedfrom the elevated and expanded diameter reaction vessel 12 and providesthe following key features:

-   -   i) Precisely controlled vertical stirring of the entire molten        bed with minimal power consumption. This facilitates circulation        of all molten metal 32 with no dead or cold spots thus enabling        maximum utilization of all the iron in the gasification process.    -   ii) Power variability in real time to accommodate changes in        feed stream heat value and thermal conversion process        interaction.    -   iii) Control of vertical stirring turbulence and speed during        the volatile thermal conversion reactions.    -   iv) Induction coil 43 protection from volatile reaction vessel        12 molten metal stirring and gasification process by isolation        of induction furnace 13 below the primary thermodynamic        reactions.    -   v) Adaptable to real time re-charging of the molten metal if the        carbon content drops too low.    -   vi) Continuous operation with varying feed stream conditions and        gasification conditions.

Vertical stirring at minimum power is accomplished by the naturalmovement of metal bath 32 caused by induction coil 43. Control of powervariability is achieved by means of a tapped transformer to vary thevoltage to coil 43. By mounting elevated, extended diameter reactionvessel 12 on top of induction furnace 13, induction coil 43 andrefractory lining 42 are isolated and thus protected from the volatilereactions of the gasification process. The superstructure of inductionfurnace 13 is specifically configured to support the weight of moltenmetal 32 and slag 33 in reaction vessel 12.

Elevated and Extended Diameter Reaction Vessel

Reactor vessel 12, or reaction chamber, is an elevated and extendeddiameter molten metal reaction section capable of sustaining efficientand stable FeO reaction during the injection of widely varyinghydrocarbon material feeds. The extended bed diameter provides enlargedmolten metal surface area and thus greater reaction zone potential. Withgreater surface area, it is also possible to inject multiple feed streamtypes and multiple process reactants requiring separate injector lancesystems 23. This greatly enhances the flexibility of the system totolerate the widely varying feed stream characteristics.

The bottom portion of elevated and extended diameter reaction vessel 12is a designed curved member. This curved member is capable of supportingthe weight of molten metal 32, slag 33, refractory lining 31, thevertical portion of reaction vessel 12, lid 11, exhaust plenum 21 andinjection lances 23 while providing superior molten metal flowcharacteristics. Larger diameter reaction vessels requiring multipleinduction furnaces, as shown in FIGS. 5 and 6, can be equipped withsquare, reinforced bottom sections to allow more uniform metal depthdistribution and reduced equipment cost.

Reaction vessel 12 can be increased in vertical capacity by addingsections between the reaction vessel 12 and lid 11 interface. Thisallows an easy, cost-effective increase of iron capacity and frothregion 34 volume for changes in feed stream composition and quantity.This design flexibility, coupled with the broad surface area permitsextensive control and use of the iron-carbon and oxygen reaction tomaintain the exothermic reaction and carbon exchange without depletingthe net carbon content of molten metal 32. Top lance 23 and sideinjection lances 37 are provided in the integrated design to accomplishthis flexibility of operation by simple modifications to reaction vessel12 design.

Refractory and insulation material for lining 31 of reaction vessel 12is specifically selected to accommodate the volatile FeO reaction,Fe-Carbon exchange and the incumbent splashing and spalling whichoccurs. This material is also used to assure minimal heat loss. Thisrefractory incorporates basic materials such as magnesia carbon brick inareas in contact with the metal bath and in proximity of the slag line.Above the slag line, where the refractory may be subject to acid,neutral, or even slightly basic conditions, a neutral refractory such asalumina or chromia-alumina spinel would be more appropriate. In off-takeregion 47 and duct areas, where temperatures will be more moderate,emphasis is placed on abrasion resistance to counteract the effect ofany carry-over particulate combined with high gas stream velocity. Thesidewall is brick while the bottom refractory is a monolithic. Therefractory is installed by means of a staggered joint configuration. Theexpanded diameter of the reaction vessel 12 allows:

-   -   i) Variable feed stream injection from multiple top injector        lances 23.    -   ii) Multiple (typically 3-6) side lance 37 injection ports to        facilitate liquid solid and gaseous feed injection in a variety        of configurations.    -   iii) Multiple side lance 37 injection ports to facilitate        stirring action in the horizontal plane of the molten bed, thus        enhancing total reaction mixing.    -   iv) Varying injection speeds due to multiple locations to        enhance and control the size and depth of the molten metal        reaction zone.    -   v) Isolation of the total reaction zone in a controllable        region.    -   vi) Increased capability to operate in the required region of        the Fe—C equilibrium chart for widely varying feed.

Slag Region

The silica slag region is purposely provided in special combinationswhich:

-   -   i) Captures and further gasifies carbon particulates escaping        the FeO-Iron-Carbon reaction.    -   ii) Captures and neutralizes certain waste gases not productive        in the synthesis gas generation process.    -   iii) Captures and neutralizes other non-carbon particulates.    -   iv) Enhances the formation of the appropriate secondary froth        reaction zone constituents to support a second synthesis gas        production area.    -   v) Coats the surrounding refractory with a protective layer as a        result of splashing from the volatile gasification reaction.    -   vi) Provides refractory design transition from molten metal to        freeboard areas of gasifying reaction vessel.

Secondary Reaction Froth Region

This section provides a volume large enough to allow control ofsecondary gasification reaction. Directly above molten metal 32 and slag33 regions, froth region 34 is typically three to fifteen times thedepth of the molten metal section, depending upon the type of mixed feedstream material involved. As previously discussed, during the injectionof hydrocarbon material and oxygen into molten metal 32, it is common toexperience a frothing or fine material expansion above molten metal 32and slag section 33. The purpose of froth region 34 is to providesufficient surface area and height, with the incumbent expandedinjection location capability, to create a controlled secondary gasreaction area which provides the following features:

-   -   i) Allows complete gasification of any hydrocarbon particulates        not fully reacted in the molten metal 32 gasification section.    -   ii) Facilitates the introduction of additional hydrocarbon fines        and reaction gases to allow additional gasification reaction and        boost synthesis gas production. These fines can include coal,        spent tires, waxes, waste oils, industrial waste chemicals, and        bio-solids.    -   iii) Provides a large transition area for changes in refractory        design and thickness.    -   iv) Allows for an extended siliceous slag 33 area and        “controlled extended” splash zone thus enhancing refractory        coating and synthesis gas production in a continuous process.    -   v) Allows for thicker slag area to accommodate additional slag        chemicals for improved synthesis gas filtration and increased        residence time.    -   vi) Permits secondary injection of by-products and waste gases        (see Table 1) to accelerate and expand synthesis gas formation.    -   vii) Permits secondary injection of gaseous reactants such as        oxygen, CO2 or water vapor to control and enhance temperature        levels and H2 and CO formation.

Expandable Off-Take Zone

Off-take zone 47 is specifically provided to allow control of the heightand intensity of froth region 34 and provide a stable transition of theexpanding synthesis gas into lid 11 and exhaust plenum 21. For some feedstream conditions, the height and extent of froth region 34 can grow toorapidly and interfere with the controlled synthesis gas production andtransition into lid 11 and plenum 21 sections. Therefore off-take zone47 is provided to allow injection of pure light gases, oxygen, carbondioxide, or water vapor to create a hot spot (or cold spot) which willplace a controlled cap or limiter to the upper extent of froth region34. Care must be taken not to inject too much oxygen orcarbon/hydrocarbon material into off-take zone 47, resulting inexcessive depletion of froth zone 34. As a result, injection intooff-take zone 47 is often an intermittent process, occurring only longenough to keep froth 34 out of exhaust plenum 21. This “capping” orstopping of froth region 34 vertical expansion is important to theoverall efficiency and control of the gasification process. This area istopped by a flanged connection to lid 11 which allows design expansionof froth region 34 and off-take region 47 due to changes in the feedstream characteristics or quantity, as well as changes in the thermalconversion process. This is accomplished simply by the addition of oneor more refractory lined circular sections between off-take region 47and lid 11. Off-take region 47 also provides an additional “pureinjection” zone for certain gaseous materials available from wasteby-products, landfills, Fischer Tropsch by-products and digesters asoutlined in Table 1.

Lid

Lid section 11 is designed to:

-   -   i) Retain the maximum amount of heat in reaction vessel 12.    -   ii) Converge escaping hot synthesis gas flow efficiently to the        exhaust plenum 21.    -   iii) Provide first level instrumentation of quality and status        of product gases.    -   iv) Resist erosion wear for particulates and high velocity gas        flow.

Lid 11 has a designed curvature which maximizes the stability of highthermal insulating refractory installation while minimizing surface flowtension and erosion characteristics. The specially selected refractorymaterial is designed to minimize heat loss for reduced thickness. Thisfacilitates maximum inside diameter and minimum exterior (outside)hole-size for exhaust plenum 21.

Exhaust Plenum

Exhaust plenum 21 is designed to provide:

-   -   i) Maximum heat retention.    -   ii) Minimum surface tension erosion characteristics.    -   iii) Minimum outside diameter.    -   iv) Efficient gas turning with minimum inside diameter (ID).    -   v) Proper gas escape velocity.    -   vi) Minimum collection of particulates and contaminants in the        turn section and downstream areas.    -   vii) Proper reaction vessel pressure.        These features provide a combined aerodynamic, thermodynamic gas        flow, characteristics needed to maximize gasification efficiency        and control. Advanced state-of-the-art thermal insulating        materials are used to extend life and maximize heat retention.

The preferred embodiments of the present invention can process andgasify a large array of mixed wastes and fuels from domestic andindustrial applications. These wastes and fuels can be contaminated witha variety of in-organics and hazardous materials. Thus, the presentinvention allows for versatility and adaptability of design toaccommodate a variation of organic and in-organic material and stillachieve high efficiency in synthesis gas production. However, this sameversatility and adaptability of design implementation can be very usefulin other applications and embodiments.

1. A gasifier comprising, an induction furnace defining a first volume,a reaction chamber configured for containing a continuous gasificationreaction, the reaction chamber defining a second volume that is indirect fluid communication with the first volume, wherein the inductionfurnace includes induction coils that are essentially isolated from thegasification reaction.
 2. The gasifier according to claim 1 wherein theinduction furnace is a coreless induction furnace.
 3. The gasifieraccording to claim 1 wherein the induction furnace is configured forvertically stirring a molten metal located within the second volume. 4.The gasifier according to claim 1 further comprising a dome-shaped lidconfigured direct the fuel gas and heat produced from the gasificationreaction to an exhaust plenum.
 5. The gasifier according to claim 4further comprising a plurality of lance receiving slots through the lidand slots through a sidewall and a bottom of the reaction chamber. 6.The gasifier according to claim 1 further comprising means forcontinuously delivering a carbonaceous fuel and reaction gases to begasified into the reaction chamber in a manner that does not project thegasification reaction into the induction furnace.
 7. The gasifieraccording to claim 1 wherein the second volume has an inside workingcircumference that is at least three times greater than an insideworking circumference of the first volume, wherein the second volumeprovides a froth gasification reaction zone directly below and integralwith an off-take zone, the froth zone being directly above a moltenmetal area and a slag area.
 8. The gasifier according to claim 1 furthercomprising two or more induction furnaces operatively coupled to abottom of the reaction chamber, each of the two or more inductionfurnaces including an interior volume that is in direct fluidcommunication with the second volume.
 9. A gasifier for the continuousproduction and collection of a fuel gas comprising, a bottom mounted ontop of an induction furnace, an opening through the bottom directlycoupling an interior of the induction furnace with an inside of thegasifier, a continuous sidewall supported by the bottom, and a topconfigured for removing the fuel gas from the gasifier.
 10. The gasifieraccording to claim 9 wherein the induction furnace is a corelessinduction furnace.
 11. The gasifier according to claim 9 wherein thebottom has an inside working circumference that is at least three timesgreater than a circumference of the opening.
 12. The gasifier accordingto claim 9 wherein the bottom is curved.
 13. The reaction chamberaccording to claim 9 wherein the induction furnace includes coils thatare isolated from a molten metal contained within the bottom.
 14. Thegasifier according to claim 9 wherein the induction furnace isconfigured for vertically stirring a molten metal contained within thebottom.
 15. The gasifier according to claim 9 wherein the bottom and theinterior of the induction furnace include a molten metal circulatedtherebetween by induction heating.
 16. The gasifier according to claim 9wherein the induction furnace is configured for maintaining atemperature of a molten metal contained within the bottom within apredetermined range during continuous gasification of a widely varyingcarbonaceous feedstock.
 17. A gasifier comprising, a reaction chamber, acarbonaceous fuel delivery member for continuously delivering acarbonaceous fuel into the reaction chamber, and an induction furnaceconfigured for continuous delivery of a molten metal into the reactionchamber.
 18. The gasifier according to claim 17 wherein, when theinduction furnace is a coreless induction furnace, the reaction chamberis integral with the induction furnace.
 19. The gasifier according toclaim 17 wherein the induction furnace is configured for continuous andcontrolled vertically stirring of the molten metal within the reactionchamber.
 20. The gasifier according to claim 17 wherein the inductionfurnace is configured for maintaining a temperature of the molten metalwithin the reaction chamber within a desired range during the continuousgasification of the carbonaceous fuel.
 21. The gasifier according toclaim 17 wherein the induction furnace is coupled to a bottom of thereaction chamber and the bottom includes an opening through which themolten metal is delivered into the reaction chamber, the opening beingat least three times smaller in circumference than the bottom.
 22. Thegasifier according to claim 17 wherein the reaction chamber includes anoff-take zone configured for controlling a height of a froth containedwithin the reaction chamber.
 23. The gasifier according to claim 17wherein the reaction chamber has an inside working volume that is atleast fifteen times greater than an inside working volume of theinduction furnace.
 24. The gasifier according to claim 17 wherein thereaction chamber includes a reaction area configured for receiving andgasifying the carbonaceous fuel, the reaction area being isolated frominduction furnace and comprised of contiguous gasification zones,starting from a bottom of the reaction chamber and moving upward,designated as a molten metal zone, a slag zone, a froth zone and anoff-take zone.
 25. The gasifier according to claim 17 wherein thereaction chamber includes at least three coreless induction furnaces,equidistantly spaced and coupled to a bottom of the reaction chamber.